1. Field of The Invention
The present invention relates to a wall structure which can be used, for example, in constructing objects such as vessels, tanks, washing towers, tubes, ships' hulls, etc. The invention also relates to a wall element for making such such a wall structure, and a method of making the wall structure.
2. The Prior Art
Norwegian Patent Specification No. 132 417 discloses an apparatus for the manufacture of sectional products of expanded plastic by extruding in such a manner that only part of the surface of the sectional product has a substantially non-expanded surface skin, whereas the remaining part of the surface of the product has substantially the same cell characteristics as the interior of the product.
The wall element used in the wall structure according to present invention has certain features in common with such an extruded section, but is different insofar as the wall element according to present invention is not a final product, but only an intermediate product for the manufacture of a greater wall structure, whereas according to Norwegian Patent Specification No. 132 417 it is a question of making ledgeformed products to be used as such. Another difference resides in that the wall element according to present invention consists of a relatively thick (about 1-10 mm) layer of solid material at the surface with a sharp transition to the expanded core, whereas according to Norwegian Patent Specification No. 132 317 it is a question of an expanded plastic which is extruded in such a manner that a relatively thin surface skin is obtained, which is practically not expanded. Here there is therefore obtained a gradual transition between the surface skin and the expanded core.
The object of the present invention is to provide a continuous wall structure for vessels, tanks, washing towers, tubes, boat hulls, etc., which is strong and simple in manufacture, the structure also readily lending itself to be given the shape of a double-curved surface and comprising an outer weather-resistant layer of reinforced plastic.